People with two common inflammatory diseases stand a higher chance of developing a heart condition that is strongly associated with stroke, a new study suggests. The study, done at the University of Arkansas for Medical Sciences, found that patients with lupus and rheumatoid arthritis have a 60 percent increased risk for atrial fibrillation, an abnormal heart rhythm (arrhythmia) linked to stroke. Pointing to a recent jump in atrial fibrillation cases, one of the study's authors said it was important to understand all the possible sources of the disease.